1. Field of the Invention
The present invention concerns an x-ray system and a method for composition of an aggregate image consisting of multiple individual images.
2. Description of the Prior Art
X-ray exposures are produced for medical diagnosis so that, for example, tissue, vascular and in particular bone structures of body parts can be considered in detail, section by section, using the x-ray images. If individual exposures are not sufficient for diagnostic, therapeutic or operative measures because they depict only a portion of the anatomy of interest, a number of x-ray exposures of the subject to be considered must be produced with a predetermined resolution. This is the case for x-ray imaging of, for example, the spinal column, a leg or an arm, since x-ray images are limited in their dimensions due to a limited detector size. Long hollow bones, the spinal column or even the imaging of a hip joint (including the femur and the knee joint to determine the leg axes, for example) cannot be imaged by means of a single x-ray exposure. When such multiple x-ray images are acquired, they must then be merged exactly with one another, or set in spatial relation to one another, corresponding to the imaged subject. Such image composition can be done, for example, with the acquisition of multiple overlapping x-ray exposures, which can then be exactly spatially associated with one another by means of correlation methods, for example. In order to successfully implement such known correlation methods, however, suitably large overlapping regions must be present. This is disadvantageous for the examination subject because more x-ray exposures must be obtained to cover the anatomy of interest that would be the case for non-overlapping exposures, and therefore a significant increase of the radiation dose to the subject occurs. Moreover, complicated correlation methods are required since few overlapping image parts of x-ray exposures contain suitable correlatable structures.